A Liquid Chromatography-Mass Spectrometry Method for the Quantification of Urinary Albumin using a Novel 15N-Isotopically Labeled Albumin Internal Standard

[摘要] Recent studies suggest that microalbuminuria confers increased cardiovascular risk, even in nondiabetic and nonhypertensive persons (1)(2). Clinically, the testing of microalbuminuria uses immunochemical methods. Controversy exists, however, regarding the accuracy of immunochemical and chromatographic methods for quantifying urine albumin (3). We earlier reported on liquid chromatography-mass spectrometry (LC-MS) for measurement of urinary albumin with bovine serum albumin (BSA) as an internal standard (4). We now report the preparation of 15N-labeled albumin as an internal standard and the validation of its use in an LC-MS assay for quantifying low concentrations of albumin in the urine of patients.The Pichia pastoris strain GS115/His+Muts (Invitrogen) was used to synthesize 15N-labeled human serum albumin (HSA) [see details in the Data Supplement that accompanies the online version of this Letter at http://www.clinchem.org/content/vol53/issue3]. A Q-TOF Premier™ mass spectrometer (Waters/Micromass) was used to characterize the 15N-labeled HSA and study its fragmentation. Loo et al. (5) previously reported the generation of source-induced fragmentation of intact proteins in an electrospray ionization source of …

[学科分类] 过敏症与临床免疫学